1. Field of the Invention
This invention relates to novel co-crystallized compositions comprising at least two acetylenic compounds, useful in measuring the time-temperature or radiation-dosage history of an article.
2. Brief Description of the Prior Art
Radiation sensitive compositions containing a polyacetylenic compound, having a minimum of two conjugated acetylenic linkages, commingled with an organic pi-acid electron acceptor are described in U.S. Pat. No. 3,501,308 (Adelman, 1970). However, compositions comprising at least two acetylenic compounds, each containing at least one --C.tbd.C--C.tbd.C-- group, are not described by the reference.
Image-receptive elements containing fixed position photosensitive crystals of polyacetylenic compounds, having at least two acetylenic linkages in a conjugated system, are described in U.S. Pat. No. 3,501,297 (Creamens, 1970). Reference is made to a mixture of 11,13-tetracosadiynedioic acid containing up to about 20 to 30 percent of monoethyl ester of 11,13-tetracosadiynedioic acid useful in an image-receptive element, but no properties are described to suggest that the compounds in the composition are co-crystallized compounds rather than being a simple mixture.
Acetylenic compounds having at least two conjugated C.tbd.C groups have been disclosed as time-temperature history indicators in U.S. Pat. No. 3,999,946. Monomeric acetylenic compounds, of the formula, R--C.tbd.C--C.tbd.C--R, where R is a monovalent radical, are colorless and are polymerizable in the solid state, either thermally or by actinic radiation. As the polymerization proceeds, these compounds undergo a contrasting color change to blue or pink and the color intensifies with time until the compounds finally develop into metallic-looking polymers. Thus, the compounds can be used as time-temperature indicators and as radiation-dosage indicators. The reference also describes polymers of the type [C.tbd.C--(CH.sub.2).sub.m OCONH(CH.sub.2).sub.6 NHOCO(CH.sub.2).sub.m --C.tbd.C].sub.n where m is 2, 3 or 4 and n is large, wherein a polymer containing polymeric repeating units of the same empirical formula, undergo color changes upon thermal annealing.